You do not need a spell to charge your wand - you could leave it out in moonlight one night to have it absorb the energy from the moon, or you could wrap it in a specific herb you enjoy using in magick to have it absorb the energy from that. Other ideas could be burying it in a graveyard, under a tree, keeping it with certain stones or herbs, annointing it with various waters of power, different oils, or passing it through blessing smokes.